The Chemistry of Extragalactic Globular Clusters

We present preliminary results of VLT/FORS spectroscopy of globular clusters in nearby early-type galaxies. Our project aims at studying the chemistry and determine the ages of globular cluster (sub-)populations. First results indicate that the different galaxies host from little to significant intermediate-age populations, and that the latter have alpha-element over iron ratios closer to solar than the old population that show an alpha-element enhancement similar to the diffuse stellar light.Comment: 4 pages (incl 2 figures) to appear in the proceedings of "Extragalactic Globular Cluster Systems", ed.M.Kissler-Patig, Springer; see also related contributions by T.H.Puzia and M.Hempel et a

Intrinsic anomalous Hall effect in nickel: An GGA+U study

The electronic structure and intrinsic anomalous Hall conductivity of nickel have been calculated based on the generalized gradient approximation (GGA) plus on-site Coulomb interaction (GGA+U) scheme. It is found that the intrinsic anomalous Hall conductivity ($\sigma_{xy}^H$) obtained from the GGA+U calculations with $U = 1.9$ eV and $J=1.2$ eV, is in nearly perfect agreement with that measured recently at low temperatures while, in contrast, the $\sigma_{xy}^H$ from the GGA calculations is about 100% larger than the measured one. This indicates that, as for the other spin-orbit interaction (SOI)-induced phenomena in 3$d$ itinerant magnets such as the orbital magnetic magnetization and magnetocrystalline anisotropy, the on-site electron-electron correlation, though moderate only, should be taken into account properly in order to get the correct anomalous Hall conductivity. The intrinsic $\sigma_{xy}^H$ and the number of valence electrons ($N_e$) have also been calculated as a function of the Fermi energy ($E_F$). A sign change is predicted at $E_F = -0.38$ eV ($N_e = 9.57$), and this explain qualitatively why the theoretical and experimental $\sigma_{xy}^H$ values for Fe and Co are positive. It is also predicted that fcc Ni$_{(1-x)}$Co(Fe,Cu)$_x$ alloys with $x$ being small, would also have the negative $\sigma_{xy}^H$ with the magnitude being in the range of $500\sim 1400$ $\Omega^{-1}$cm$^{-1}$. The most pronounced effect of including the on-site Coulomb interaction is that all the $d$-dominant bands are lowered in energy relative to the $E_F$ by about 0.3 eV, and consequently, the small minority spin X$_2$ hole pocket disappears. The presence of the small X$_2$ hole pocket in the GGA calculations is attributed to be responsible for the large discrepancy in the $\sigma_{xy}^H$ between theory and experiment.Comment: 7 pages, 3 figures; Accepted for publication in Physical Review

Properties of 3-manifolds for relativists

In canonical quantum gravity certain topological properties of 3-manifolds are of interest. This article gives an account of those properties which have so far received sufficient attention, especially those concerning the diffeomorphism groups of 3-manifolds. We give a summary of these properties and list some old and new results concerning them. The appendix contains a discussion of the group of large diffeomorphisms of the $l$-handle 3-manifold.Comment: 20 pages. Plain-TeX, no figures, 1 Table (A4 format

Why the Realist-Instrumentalist Debate about Rational Choice Rests on a Mistake

Within the social sciences, much controversy exists about which status should be ascribed to the rationality assumption that forms the core of rational choice theories. Whilst realists argue that the rationality assumption is an empirical claim which describes real processes that cause individual action, instrumentalists maintain that it amounts to nothing more than an analytically set axiom or ‘as if’ hypothesis which helps in the generation of accurate predictions. In this paper, I argue that this realist-instrumentalist debate about rational choice theory can be overcome once it is realised that the rationality assumption is neither an empirical description nor an ‘as if’ hypothesis, but a normative claim

Pharmacokinetics of Micafungin in Critically Ill Patients

We investigated covariates of pharmacokinetics of micafungin in critically ill patients. After application of micafungin, plasma samples were collected. Non-linear mixed effects modelling (NONMEM 7.3) was used to develop the pharmacokinetic model. Using this model, the adequacy of a fixed 100 mg dosing regimen was evaluated in the study cohort. A two-compartment model with linear elimination was found to describe the obtained data. SOFA score was identified as a significant covariate on both clearance and central volume of distribution, respectively. Patients in highly critical condition, represented by a SOFA above 10 showed a 30.8% lower central volume of distribution than the less critically ill patients. For patients with bilirubin levels above 4 mg/dl, clearance was decreased by 21.1%. Renal replacement therapy (RRT) did not influence micafungin clearance or the volumes of distribution. In a posthoc evaluation of the modeled population, 100 mg micafungin was suitable when assessing the PKPD targets (AUC/MIC) for C. albicans and C. glabrata, with insufficient target attainment for C. parapsilosis. Micafungin pharmacokinetics appear not to be influenced by the status of RRT. A dose of 100 mg micafungin is suitable for infections with C. albicans and C. glabrata in critically ill patients

Massive open star clusters using the VVV survey III: A young massive cluster at the far edge of the Galactic bar

Context: Young massive clusters are key to map the Milky Way's structure, and near-IR large area sky surveys have contributed strongly to the discovery of new obscured massive stellar clusters. Aims: We present the third article in a series of papers focused on young and massive clusters discovered in the VVV survey. This article is dedicated to the physical characterization of VVV CL086, using part of its OB-stellar population. Methods: We physically characterized the cluster using $JHK_S$ near-infrared photometry from ESO public survey VVV images, using the VVV-SkZ pipeline, and near-infrared $K$-band spectroscopy, following the methodology presented in the first article of the series. Results: Individual distances for two observed stars indicate that the cluster is located at the far edge of the Galactic bar. These stars, which are probable cluster members from the statistically field-star decontaminated CMD, have spectral types between O9 and B0V. According to our analysis, this young cluster ($1.0$ Myr $<$ age $< 5.0$ Myr) is located at a distance of $11^{+5}_{-6}$ kpc, and we estimate a lower limit for the cluster total mass of $(2.8^{+1.6}_{-1.4})\cdot10^3 {M}_{\odot}$. It is likely that the cluster contains even earlier and more massive stars.Comment: Accepted for publication as a Letter in A&

New galactic star clusters discovered in the VVV survey : Candidates projected on the inner disk and bulge

Context. VISTA Variables in the Vía Láctea (VVV) is one of six ESO Public Surveys using the 4 meter Visible and Infrared Survey Telescope for Astronomy (VISTA). The VVV survey covers the Milky Way bulge and an adjacent section of the disk, and one of the principal objectives is to search for new star clusters within previously unreachable obscured parts of the Galaxy. Aims. The primary motivation behind this work is to discover and analyze obscured star clusters in the direction of the inner Galactic disk and bulge. Methods. Regions of the inner disk and bulge covered by the VVV survey were visually inspected using composite JHKS color images to select new cluster candidates on the basis of apparent overdensities. DR1, DR2, CASU, and point spread function photometry of 10 × 10 arcmin fields centered on each candidate cluster were used to construct color-magnitude and color-color diagrams. Follow-up spectroscopy of the brightest members of several cluster candidates was obtained in order to clarify their nature. Results. We report the discovery of 58 new infrared cluster candidates. Fundamental parameters such as age, distance, and metallicity were determined for 20 of the most populous clusters.Peer reviewedFinal Accepted Versio

The rapidly oscillating Ap star HD 99563 and its distorted dipole pulsation mode

We undertook a time-series photometric multi-site campaign for the rapidly oscillating Ap star HD 99563 and also acquired mean light observations over two seasons. The pulsations of the star, that show flatter light maxima than minima, can be described with a frequency quintuplet centred on 1557.653 microHertz and some first harmonics of these. The amplitude of the pulsation is modulated with the rotation period of the star that we determine with 2.91179 +/- 0.00007 d from the analysis of the stellar pulsation spectrum and of the mean light data. We break the distorted oscillation mode up into its pure spherical harmonic components and find it is dominated by the l=1 pulsation, and also has a notable l=3 contribution, with weak l=0 and 2 components. The geometrical configuration of the star allows one to see both pulsation poles for about the same amount of time; HD 99563 is only the fourth roAp star for which both pulsation poles are seen and only the third where the distortion of the pulsation modes was modelled. We point out that HD 99563 is very similar to the well-studied roAp star HR 3831. Finally, we note that the visual companion of HD 99563 is located in the Delta Scuti instability strip and may thus show pulsation. We show that if the companion was physical, the roAp star would be a 2.03 solar mass object, seen at a rotational inclination of 44 degrees, which then predicts a magnetic obliquity of 86.4 degrees.Comment: 10 pages, 6 figures, accepted for publication by MNRA

VVV-WIT-01: highly obscured classical nova or protostellar collision?

© 2020 The Author(s).A search of the first Data Release of the VISTA Variables in the Via Lactea (VVV) Survey discovered the exceptionally red transient VVV-WIT-01 (H-Ks=5.2). It peaked before March 2010, then faded by ~9.5 mag over the following two years. The 1.6-22 µm spectral energy distribution in March 2010 was well fit by a highly obscured black body with T ~ 1000 K and AKs ~ 6.6 mag. The source is projected against the Infrared Dark Cloud (IRDC) SDC G331.062-0.294. The chance projection probability is small for any single event (p ≈ 0.01 to 0.02) which suggests a physical association, e.g. a collision between low mass protostars. However, black body emission at T ~ 1000 K is common in classical novae (especially CO novae) at the infrared peak in the light curve, due to condensation of dust ~30-60 days after the explosion. Radio follow up with the Australia Telescope Compact Array (ATCA) detected a fading continuum source with properties consistent with a classical nova but probably inconsistent with colliding protostars. Considering all VVV transients that could have been projected against a catalogued IRDC raises the probability of a chance association to p=0.13 to 0.24. After weighing several options, it appears likely that VVV-WIT-01 was a classical nova event located behind an IRDC.Peer reviewedFinal Published versio